As Bitcoin becomes an increasingly popular form of digital cash, the cryptocurrency is being accepted in exchange for everything from socks to sushi to heroin. If one anarchist has his way, it'll soon be used to buy murder, too.

Last month I received an encrypted email from someone calling himself by the pseudonym Kuwabatake Sanjuro, who pointed me towards his recent creation: The website Assassination Market, a crowdfunding service that lets anyone anonymously contribute bitcoins towards a bounty on the head of any government official--a kind of Kickstarter for political assassinations. According to Assassination Market's rules, if someone on its hit list is killed--and yes, Sanjuro hopes that many targets will be--any hitman who can prove he or she was responsible receives the collected funds.

For now, the site's rewards are small but not insignificant. In the four months that Assassination Market has been online, six targets have been submitted by users, and bounties have been collected ranging from ten bitcoins for the murder of NSA director Keith Alexander and 40 bitcoins for the assassination of President Barack Obama to 124.14 bitcoins--the largest current bounty on the site--targeting Ben Bernanke, chairman of the Federal Reserve and public enemy number one for many of Bitcoin's anti-banking-system users. At Bitcoin's current rapidly rising exchanges rate, that's nearly $75,000 for Bernanke's would-be killer.

Sanjuro's grisly ambitions go beyond raising the funds to bankroll a few political killings. He believes that if Assassination Market can persist and gain enough users, it will eventually enable the assassinations of enough politicians that no one would dare to hold office. He says he intends Assassination Market to destroy "all governments, everywhere."

"I believe it will change the world for the better," writes Sanjuro, who shares his handle with the nameless samurai protagonist in the Akira Kurosawa film "Yojimbo." (He tells me he chose it in homage to the creator of the online black market Silk Road, who called himself the Dread Pirate Roberts, as well Bitcoin inventor Satoshi Nakamoto.) "Thanks to this system, a world without wars, dragnet panopticon-style surveillance, nuclear weapons, armies, repression, money manipulation, and limits to trade is firmly within our grasp for but a few bitcoins per person. I also believe that as soon as a few politicians gets offed and they realize they've lost the war on privacy, the killings can stop and we can transition to a phase of peace, privacy and laissez-faire."

I contacted the Secret Service and the FBI to ask if they're investigating Assassination Market, and both declined to comment.

Like other so-called "dark web" sites, Assassination Market runs on the anonymity network Tor, which is designed to prevent anyone from identifying the site's users or Sanjuro himself. Sanjuro's decision to accept only Bitcoins is also intended to protect users, Sanjuro, and any potential assassins from being identified through their financial transactions. Bitcoins, after all, can be sent and received without necessarily tying them to any real-world identity. In the site's instructions to users, Sanjuro suggests they run their funds through a "laundry" service to make sure the coins are anonymized before contributing them to anyone's murder fund.

As for technically proving that an assassin is responsible for a target's death, Assassination Market asks its killers to create a text file with the date of the death ahead of time, and to use a cryptographic function known as a hash to convert it to a unique string of characters. Before the murder, the killer then embeds that data in a donation of one bitcoin or more to the victim's bounty. When a target is successfully murdered, he or she can send Sanjuro the text file, which Sanjuro hashes to check that the results match the data sent before the target's death. If the text file is legitimate and successfully predicted the date of the killing, the sender must have been responsible for the murder, according to Sanjuro's logic. Sanjuro says he'll keep one percent of the payout himself as a commission for his services.

Just reading about that coldly calculative system of lethal violence likely inspires queasy feelings or outrage. But Sanjuro says that the public's abhorrence won't prevent the system from working. And as a matter of ethics, he notes that he'll accept only user-suggested targets "who have initiated force against other humans. More specifically, only people who are outside the reach of the law because it has been subverted and corrupted, and whose victims have no other way to take revenge than to do so anonymously."

Even setting aside the immorality of killing, doesn't the notion of enabling small minorities of angry Bitcoin donors to assassinate elected officials sound like an attempt to cripple democracy? "Of course, limiting democracy is why we even have a constitution," Sanjuro responds. "Majority support does not make a leader legitimate any more than it made slavery legitimate. With this market the great equalising forces of capitalism have the opportunity to work in politics too. One bitcoin paid is one vote closer to a veto of whatever legislation you dislike."

Sanjuro didn't actually invent the concept of an anonymous crowdfunded assassination market. The idea dates back to the cypherpunk movement of the mid-1990s, whose adherents dreamt of using encryption tools to weaken the government and empower individuals. Former
Intel engineer and Cypherpunk Mailing List founder Tim May argued that uncrackable secret messages and untraceable digital currency would lead to assassination markets in his "Cryptoanarchist's Manifesto" written in 1992.

A few years later, another former Intel engineer named Jim Bell proposed a system of funding assassinations through encrypted, anonymous donations in an essay he called "Assassination Politics." The system he described closely matches Sanjuro's scheme, though anonymity tools like Tor and Bitcoin were mostly theoretical at the time. As Bell wrote then:

If only 0.1% of the population, or one person in a thousand, was willing to pay $1 to see some government slimeball dead, that would be, in effect, a $250,000 bounty on his head. Further, imagine that anyone considering collecting that bounty could do so with the mathematical certainty that he could not be identified, and could collect the reward without meeting, or even talking to, anybody who could later identify him. Perfect anonymity, perfect secrecy, and perfect security. And that, combined with the ease and security with which these contributions could be collected, would make being an abusive government employee an extremely risky proposition. Chances are good that nobody above the level of county commissioner would even risk staying in office.

Bell would later serve years in prison for tax evasion and stalking a federal agent, and was only released in March of 2012. When I contacted him by email, he denied any involvement in Sanjuro's Assassination Market and declined to comment on it.

Sanjuro tells me he's long been aware of Bell's idea. But he only decided to enact it after the past summer's revelations of mass surveillance by the NSA exposed in a series of leaks by agency contractor Edward Snowden. "Being forced to alter my every happy memory during internet activity, every intimate moment over the phone with my loved ones, to also include some of the people I hate the most listening in, analysing the conversation, was the inspiration I needed to embark on this task," he writes. "After about a week of muttering 'they must all die' under my breath every time I opened a newspaper or turned on the television, I decided something had to be done. This is my contribution to the cause."

Assassination Market isn't the first online service to suggest funding murder with bitcoins. Other Tor-hidden websites with names like Quick Kill, Contract Killer and C'thulhu have all claimed to offer murders in exchange for bitcoin payments. But none of them responded to my attempts to contact their administrators, and all required advanced payments for their services, so they may be scams.

And how do Assassination Market's users know that it's not a similar fraud scheme designed to steal users' bitcoins? "You don't," Sanjuro admits. But he argues that if it were a scam, it would be a very complex and risky one, given that even threatening to harm the president of the United States is a felony.

Kuwabatake Sanjuro, the ronin samurai in the film "Yojimbo" whose pseudonym the Assassination Market's founder has adopted.

Other than that, "I can but appeal personally," Sanjuro writes. "I live a comfortable, albeit somewhat spartan life, and the only thing that really pains me is the increasing attacks on the liberties I enjoy in my daily life, mainly my personal privacy. I cannot buy that with money, so I have no need of it. There is nothing I want more than to see this project succeed, and for that I need dead politicians."

Sanjuro counters that in addition to Tor, Bitcoin, and the usual encryption tools, he has "measures in place to prevent the effectiveness of such an arrest. Naturally these will have to be kept secret."

He adds that, like an earlier generation of cypherpunks, he puts his faith in the mathematical promise of cryptography to trump the government's power to stop him. "With cryptography, the state, or any protection firm, is largely obsolete...all activity that can be reduced to information transfer will be completely out of the government's, or anyone's, hands, other than the parties involved," he says.

I'm a technology, privacy, and information security reporter and most recently the author of the book This Machine Kills Secrets, a chronicle of the history and future of information leaks, from the Pentagon Papers to WikiLeaks and beyond.